`TestAccelerateRegionsScheduleInRanges` is flaky

[rleungx]

Flaky Test

Which jobs are failing

=== NAME  TestRegionTestSuite/TestAccelerateRegionsScheduleInRanges
    region_test.go:208: 
        	Error Trace:	/home/runner/work/pd/pd/tests/server/api/region_test.go:208
        	            				/home/runner/work/pd/pd/tests/testutil.go:363
        	            				/home/runner/work/pd/pd/tests/testutil.go:323
        	            				/home/runner/work/pd/pd/tests/server/api/region_test.go:176
        	Error:      	"[%!s(uint64=555) %!s(uint64=554) %!s(uint64=552) %!s(uint64=[551](https://github.com/tikv/pd/actions/runs/10052092705/job/27782746919#step:4:552)) %!s(uint64=556) %!s(uint64=553)]" should have 4 item(s), but has 6
        	Test:       	TestRegionTestSuite/TestAccelerateRegionsScheduleInRanges

CI link

https://github.com/tikv/pd/actions/runs/10052092705/job/27782746919

Reason for failure (if possible)

Anything else